204 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



21. German Notes. 



By Hertholi) Ribbkntrop, CLE. 



In the Transac/iofis for July 1911 (vol. xxiv., p. 203) we 

 described the experiments made by Oberforster Haak, of the 

 Mycological Laboratory in Eberswalde, in regard to the artificial 

 culture of the pine-leaf scab, and his observations on the 

 formation of the apothecia (or fruits) of this fell disease. 



The laboratory results explained to a great extent the course 

 of the disease in pine forests, and permitted a critical 

 examination of the generally accepted views regarding pine 

 scab, and of the question how far the measures adopted for its 

 prevention and extermination ^\q prima facie correct. 



With this aim in view, Haak placed pattern areas under 

 constant observation and kept a separate ledger for each case. 

 These areas embraced strongly diseased cultures with plants 

 from I to 10 years old, thickets of 20 to 25 years old, 30 to 

 40-year-old pole forests, and mature forests. 



He also observed the progress of the disease on plants 

 artificially nfected each year. These plants he raised for the 

 purpose in a garden unquestionably free from all suspicion of 

 nfection, or obtained from the disease-free nursery at Chorin. 



He laid down that, in order to arrive at a satisfactory 

 explanation regarding the nature and progress of the destructive 

 scab disease in pine nurseries and cultures, a satisfactory reply 

 must be forthcoming to the two questions : Whence, and at 

 what time, do the germs of the disease enter the plants? 



It is evident that the correct answer to these two questions 

 forms the very foundation of the biology of LopJiodermiuin 

 pinastri, and of all the measures adopted to counteract its 

 ravages, but our most eminent researchers and authors have 

 hitherto contradicted each other in regard to them. 



The late Prof. Mayr, of Munich, made some experimental 

 cultures at Geisenfeld by Ingolstadt. He collected a quantity 

 of dead pine leaves in mature and pole forests, and an equal 

 amount from an infected young cultivation, and spread them on 

 separate pattern areas, in June 1902. Those covered with 

 litter out of the mature forests developed no sign of the disease, 

 whereas the plants in the area in which the leaves of infected 

 young growth had been used became thoroughly diseased. 



